Purity >98%. Glycinamide ribonucleotide formyltransferase (GART) is a folate-dependent enzyme required for de novo purine synthesis. Lometrexol is a folate analog antimetabolite with antineoplastic activity. At nanomolar conentrations, it inhibits GART preventing de novo purine synthesis, inhibiting DNA synthesis, arresting cells in the S phase of the cell cycle, and inhibiting tumor cell proliferation.